Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$168.72	10.139%	$185.8265	$185.83	$185.85	$185.80
Purchase #2	$132.41	6.657%	$141.2245	$141.22	$141.20	$141.20
Purchase #3	$61.46	3.832%	$63.8151	$63.82	$63.80	$63.80
Purchase #4	$59.74	8.318%	$64.7092	$64.71	$64.70	$64.70
Purchase #5	$80.91	7.340%	$86.8488	$86.85	$86.85	$86.80
Purchase #6	$247.79	10.277%	$273.2554	$273.26	$273.25	$273.30
Purchase #7	$150.33	4.386%	$156.9235	$156.92	$156.90	$156.90
7 purchase totals =	$901.36		$972.6030	$972.61	$972.55	$972.50